2.1. Field of the Technology
The present technology relates to one or more of the detection, diagnosis, treatment, prevention and amelioration of respiratory-related disorders. In particular, the present technology relates to medical devices or apparatus, and their use. Such devices may include an interface for directing a treatment to a patient respiratory system.
2.2. Description of the Related Art
The respiratory system of the body facilitates gas exchange. The nose and mouth form the entrance to the airways of a patient.
The airways consist of a series of branching tubes, which become narrower, shorter and more numerous as they penetrate deeper into the lung. The prime function of the lung is gas exchange, allowing oxygen to move from the air into the venous blood and carbon dioxide to move out. The trachea divides into right and left main bronchi, which further divide eventually into terminal bronchioles. The bronchi make up the conducting airways, and do not take part in gas exchange. Further divisions of the airways lead to the respiratory bronchioles, and eventually to the alveoli. The alveolated region of the lung is where the gas exchange takes place, and is referred to as the respiratory zone. See “Respiratory Physiology”, by John B. West, Lippincott Williams & Wilkins, 9th edition published 2011.
A range of respiratory disorders exist.
Obstructive Sleep Apnoea (OSA), a form of Sleep Disordered Breathing (SDB), is characterized by occlusion of the upper air passage during sleep. It results from a combination of an abnormally small upper airway and the normal loss of muscle tone in the region of the tongue, soft palate and posterior oropharyngeal wall during sleep. The condition causes the affected patient to stop breathing for periods typically of 30 to 120 seconds duration, sometimes 200 to 300 times per night. It often causes excessive daytime somnolence, and it may cause cardiovascular disease and brain damage. The syndrome is a common disorder, particularly in middle aged overweight males, although a person affected may have no awareness of the problem. See U.S. Pat. No. 4,944,310 (Sullivan).
Cheyne-Stokes Respiration (CSR) is a disorder of a patient's respiratory controller in which there are rhythmic alternating periods of waxing and waning ventilation, causing repetitive de-oxygenation and re-oxygenation of the arterial blood. It is possible that CSR is harmful because of the repetitive hypoxia. In some patients CSR is associated with repetitive arousal from sleep, which causes severe sleep disruption, increased sympathetic activity, and increased afterload. See U.S. Pat. No. 6,532,959 (Berthon-Jones).
Obesity Hyperventilation Syndrome (OHS) is defined as the combination of severe obesity and awake chronic hypercapnia, in the absence of other known causes for hypoventilation. Symptoms include dyspnea, morning headache and excessive daytime sleepiness.
Chronic Obstructive Pulmonary Disease (COPD) encompasses any of a group of lower airway diseases that have certain characteristics in common. These include increased resistance to air movement, extended expiratory phase of respiration, and loss of the normal elasticity of the lung. Examples of COPD are emphysema and chronic bronchitis. COPD is caused by chronic tobacco smoking (primary risk factor), occupational exposures, air pollution and genetic factors. Symptoms include: dyspnoea on exertion, chronic cough and sputum production.
Neuromuscular Disease (NMD) may encompass many diseases and ailments that impair the functioning of the muscles either directly via intrinsic muscle pathology, or indirectly via nerve pathology. Some NMD patients are characterised by progressive muscular impairment leading to loss of ambulation, being wheelchair-bound, swallowing difficulties, respiratory muscle weakness and, eventually, death from respiratory failure. Neuromuscular disorders can be divided into rapidly progressive and slowly progressive: (i) Rapidly progressive disorders: Characterised by muscle impairment that worsens over months and results in death within a few years (e.g. Amyotrophic lateral sclerosis (ALS) and Duchenne muscular dystrophy (DMD) in teenagers); (ii) Variable or slowly progressive disorders: Characterised by muscle impairment that worsens over years and only mildly reduces life expectancy (e.g. Limb girdle, Facioscapulohumeral and Myotonic muscular dystrophy). Symptoms of respiratory failure in NMD include: increasing generalised weakness, dysphagia, dyspnoea on exertion and at rest, fatigue, sleepiness, morning headache, and difficulties with concentration and mood changes.
Chest wall disorders are a group of thoracic deformities that result in inefficient coupling between the respiratory muscles and the thoracic cage. The disorders are usually characterised by a restrictive defect and share the potential of long term hypercapnic respiratory failure. Scoliosis and/or kyphoscoliosis may cause severe respiratory failure. Symptoms of respiratory failure include: dyspnoea on exertion, peripheral oedema, orthopnoea, repeated chest infections, morning headaches, fatigue, poor sleep quality and loss of appetite.
Otherwise healthy individuals may take advantage of systems and devices to prevent respiratory disorders from arising.
2.2.1 Therapy
Nasal Continuous Positive Airway Pressure (CPAP) therapy has been used to treat Obstructive Sleep Apnea (OSA). The hypothesis is that continuous positive airway pressure acts as a pneumatic splint and may prevent upper airway occlusion by pushing the soft palate and tongue forward and away from the posterior oropharyngeal wall.
Non-invasive ventilation (NIV) provides ventilator support to a patient through the upper airways to assist the patient in taking a full breath and/or maintain adequate oxygen levels in the body by doing some or all of the work of breathing. The ventilator support is provided via a patient interface. NIV has been used to treat CSR, OHS, COPD, MD and Chest Wall disorders.
Invasive ventilation (IV) provides ventilatory support to patients that are no longer able to effectively breathe themselves and is provided using a tracheostomy tube.
Ventilators may control the timing and pressure of breaths pumped into the patient and monitor the breaths taken by the patient. The methods of control and monitoring patients typically include volume-cycled and pressure-cycled methods. The volume-cycled methods may include among others, Pressure-Regulated Volume Control (PRVC), Volume Ventilation (VV), and Volume Controlled Continuous Mandatory Ventilation (VC-CMV) techniques. The pressure-cycled methods may involve, among others, Assist Control (AC), Synchronized Intermittent Mandatory Ventilation (SIMV), Controlled Mechanical Ventilation (CMV), Pressure Support Ventilation (PSV), Continuous Positive Airway Pressure (CPAP), or Positive End Expiratory Pressure (PEEP) techniques.
2.2.2 Systems
One known device used for treating sleep disordered breathing is the S9 Sleep Therapy System, manufactured by ResMed. Ventilators such as the ResMed Stellar™ Series of Adult and Paediatric Ventilators may provide support for invasive and non-invasive non-dependent ventilation for a range of patients for treating a number of conditions such as but not limited to NMD, OHS and COPD.
The ResMed Elisée™ 150 ventilator and ResMed VS III™ ventilator may provide support for invasive and non-invasive dependent ventilation suitable for adult or paediatric patients for treating a number of conditions. These ventilators provide volumetric and barometric ventilation modes with a single or double limb circuit.
A system may comprise a PAP Device/ventilator, an air circuit, a humidifier, a patient interface, and data management.
2.2.3 Patient Interface
A patient interface may be used to interface respiratory equipment to its user, for example by providing a flow of breathable gas. The flow of breathable gas may be provided via a mask to the nose and/or mouth, a tube to the mouth or a tracheostomy tube to the trachea of the user. Depending upon the therapy to be applied, the patient interface may form a seal, e.g. with a face region of the patient, to facilitate the delivery of gas at a pressure at sufficient variance with ambient pressure to effect therapy, e.g. a positive pressure of about 10 cmH2O. For other forms of therapy, such as the delivery of oxygen, the patient interface may not include a seal sufficient to facilitate delivery to the airways of a supply of gas at a positive pressure of about 10 cm H2O.
The design of a patient interface presents a number of challenges. The face has a complex three-dimensional shape. The size and shape of noses varies considerably between individuals. Since the head includes bone, cartilage and soft tissue, different regions of the face respond differently to mechanical forces. The jaw or mandible may move relative to other bones of the skull. The whole head may move during the course of a period of respiratory therapy.
As a consequence of these challenges, some masks suffer from being one or more of obtrusive, aesthetically undesirable, costly, poorly fitting, difficult to use, and uncomfortable especially when worn for long periods of time or when a patient is unfamiliar with a system. For example, masks designed solely for aviators, mask designed as part of personal protection equipment (e.g. filter masks), SCUBA masks, or for the administration of anaesthetics may be tolerable for their original application, but nevertheless be undesirably uncomfortable to be worn for extended periods of time, e.g. several hours. This is even more so if the mask is to be worn during sleep. An uncomfortable mask may impact on patient compliance.
Nasal CPAP therapy is highly effective to treat certain respiratory disorders, provided patients comply with therapy. If a mask is uncomfortable, or difficult to use a patient may not comply with therapy. Since it is often recommended that a patient regularly wash their mask, if a mask is not easily replaceable or difficult to clean (e.g. difficult to assemble or disassemble), patients may not replace or clean their mask and this may impact on patient compliance.
For these reasons, masks for delivery of nasal CPAP during sleep form a distinct field.
2.2.3.1 Seal-Forming Portion
Patient interfaces may include a seal-forming portion.
A patient interface may be partly characterised according to the design intent of where the seal-forming portion is to engage with the face in use. In one form of patient interface, a seal-forming portion may comprise two sub-portions to engage with respective left and right nares. In one form of patient interface, a seal-forming portion may comprise a single element that surrounds both nares in use. Such single element may be designed to for example overlay an upper lip region and a nasal bridge region of a face. In one form of patient interface a seal-forming portion may comprise an element that surrounds a mouth region in use, e.g. by forming a seal on a lower lip region of a face. In one form of patient interface, a seal-forming portion may comprise a single element that surrounds both nares and a mouth region in use. These different types of patient interfaces may be known by a variety of names by their manufacturer including nasal masks, full-face masks, nasal pillows, nasal puffs and oro-nasal masks.
One type of seal-forming portion extends around the periphery of the patient interface, and is intended to seal against the user's face when force is applied to the patient interface with the seal-forming portion in confronting engagement with the user's face. The seal-forming portion may consist of an air or fluid filled cushion, or a moulded or formed surface of a resilient seal element made of an elastomer such as a rubber. With this type of seal-forming portion, if the fit is not adequate, there will be gaps between the seal-forming portion and the face, and additional force will be required to force the patient interface against the face in order to achieve a seal.
Another type of seal-forming portion incorporates a flap seal of thin material so positioned about the periphery of the mask so as to provide a self-sealing action against the face of the user when positive pressure is applied within the mask. Like the previous style of seal forming portion, if the match between the face and the mask is not good, additional force may be required to effect a seal, or the mask may leak. Furthermore, if the shape of the seal-forming portion does not match that of the patient, it may crease or buckle in use, giving rise to leaks.
Another type of seal-forming portion may comprise a friction-fit element, e.g. for insertion into a naris.
Another form of seal-forming portion may use adhesive to effect a seal. Some patients may find it inconvenient to constantly apply and remove an adhesive to their face.
A range of patient interface seal-forming portion technologies are disclosed in the following patent applications, assigned to ResMed Limited: WO 1998/004,310; WO 2006/074,513; WO 2010/135,785.
2.2.3.2 Positioning and Stabilising
A seal-forming portion of a patient interface used for positive air pressure therapy is subject to the corresponding force of the air pressure to disrupt a seal. Thus a variety of techniques have been used to position the seal-forming portion, and to maintain it in sealing relation with the appropriate portion of the face.
One technique is the use of adhesives. See for example US Patent publication US 2010/0000534.
Another technique is the use of one or more straps and stabilising harnesses. Many such harnesses suffer from being one or more of ill-fitting, bulky, uncomfortable and awkward to use.
2.2.3.3 Vent Technologies
Some forms of patient interface systems may include a vent to allow the washout of exhaled carbon dioxide. Many such vents are noisy. Others may block in use and provide insufficient washout. Some vents may be disruptive of the sleep of a bed-partner 1100 of the patient 1000, e.g. through noise or focussed airflow.
ResMed Limited has developed a number of improved mask vent technologies. See WO 1998/034,665; WO 2000/078,381; U.S. Pat. No. 6,581,594; US Patent Application; US 2009/0050156; US Patent Application 2009/0044808.
Table of noise of prior masks (ISO 17510-2:2007, 10 cm H2O pressure at 1 m)A-weightedA-weightedsound powersound Masklevel dBApressure dBA Mask nametype(uncertainty)(uncertainty)Year (approx.)Glue-on (*)nasal50.942.91981ResCare standard (*)nasal31.523.51993ResMed Mirage (*)nasal29.521.51998ResMed UltraMiragenasal36 (3)28 (3)2000ResMed Mirage Activanasal32 (3)24 (3)2002ResMed Mirage Micronasal30 (3)22 (3)2008ResMed Mirage SoftGelnasal29 (3)22 (3)2008ResMed Mirage FXnasal26 (3)18 (3)2010ResMed Mirage Swift (*)nasal pillows37  29  2004ResMed Mirage Swift IInasal pillows28 (3)20 (3)2005ResMed Mirage Swift LTnasal pillows25 (3)17 (3)2008ResMed Mirage series I, II (*)full face31.723.72000ResMed UltraMiragefull face35 (3)27 (3)2004ResMed Mirage Quattrofull face26 (3)18 (3)2006ResMed Mirage Quattro FXfull face27 (3)19 (3)2008(* one specimen only, measured using test method specified in ISO3744 in CPAP mode at 10 cm H2O)
Sound pressure values of a variety of objects are listed below
A-weighted soundObjectpressure dB (A)NotesVacuum cleaner: Nilfisk 68ISO3744 at 1 mWalter Broadly Litter distanceHog: B+ GradeConversational speech601 m distanceAverage home50Quiet library40Quiet bedroom at night30Background in TV studio202.2.3.4 Nasal Pillow Technologies
One form of nasal pillow is found in the Adam Circuit manufactured by Puritan Bennett. Another nasal pillow, or nasal puff is the subject of U.S. Pat. No. 4,782,832 (Trimble et al.), assigned to Puritan-Bennett Corporation.
ResMed Limited has manufactured the following products that incorporate nasal pillows: SWIFT nasal pillows mask, SWIFT II nasal pillows mask, SWIFT LT nasal pillows mask, SWIFT FX nasal pillows mask and LIBERTY full-face mask. The following patent applications, assigned to ResMed Limited, describe nasal pillows masks: International Patent Application WO2004/073,778 (describing amongst other things aspects of ResMed SWIFT nasal pillows), U.S. Patent Application 2009/0044808 (describing amongst other things aspects of ResMed SWIFT LT nasal pillows); International Patent Applications WO 2005/063,328 and WO 2006/130,903 (describing amongst other things aspects of ResMed LIBERTY full-face mask); International Patent Application WO 2009/052,560 (describing amongst other things aspects of ResMed SWIFT FX nasal pillows).
2.2.4 Respiratory Apparatus (PAP Device/Ventilator)
Examples of respiratory apparatuses include ResMed's S9 AutoSet™ PAP device and ResMed's Stellar™ 150 ventilator. PAP devices or ventilators typically comprise a flow generator, such as a motor-driven blower or a compressed gas reservoir, and are configured to provide a controlled supply of breathable gases (e.g., air) to the airway of a patient. In some cases, the flow of air or other breathable gases may be supplied to the airway of the patient at positive pressure may be supplied to the airway of a patient by a PAP device such as a motor-driven blower. The outlet of the blower PAP device or the ventilator is connected via a flexible delivery conduit an air circuit to a patient interface such as those described above.
Ventilators or PAP devices typically include a flow generator, an inlet filter, a patient interface, an air circuit delivery conduit connecting the flow generator to the patient interface, various sensors and a microprocessor-based controller. The patient interface may include a mask or a tracheostomy tube as described above. The flow generator may include a servo-controlled motor, volute and an impeller that forms a blower. In some cases a brake for the motor may be implemented to more rapidly reduce the speed of the blower so as to overcome the inertia of the motor and impeller. The braking can permit the blower to more rapidly achieve a lower pressure condition in time for synchronization with expiration despite the inertia. In some cases the flow generator may also include a valve capable of discharging generated air to atmosphere as a means for altering the pressure delivered to the patient as an alternative to motor speed control. The sensors measure, amongst other things, motor speed, mass flow rate and outlet pressure, such as with a pressure transducer or the like. The apparatus may optionally include a humidifier and/or heater elements in the path of the air delivery circuit. The controller may include data storage capacity with or without integrated data retrieval and display functions.